2009/12/06 Linux Kernel Podcast
Audio: http://media.libsyn.com/media/jcm/linux_kernel_podcast_20091206.mp3
For the weekend of December 6th, 2009, I’m Jon Masters with a summary of today’s LKML traffic.
In today’s issue: BKL, cgroups, constants, sh, and tracing.
BKL. Thomas Gleixner posted a series of “BKL removal” patches for drivers, core, and individual architectures. As a side effect of this work, Thomas introduces the raw_spinlock as used in the RT kernel, which on non-RT platforms are identical to the non-raw versions (the non-raw versions map directly onto the new raw_spinlock). The Big Kernel Lock will outlive 2.6.33, but hopefully Thomas and others will decrease the in-kernel usage thereof.
Cgroups. Ben Blum (CMU) posted an interesting series of patches intended to implement modularization support for “building, loading, and unloading subsystems [cgroups] as modules”. He notes this is an iteration of a previous patch for which he provides a link. On a tangent, Jens Axboe noted that the latest block bits for 2.6.33 include the cgroup-based blk-io controller (in addition to other cool stuff, such as the final mainlining of DRBD – the Distributed Replicating Block Device that has existed out-of-tree and has been shipped by at least one Linux vendor for a number of years).
Constants. Emese Revfy posted thirty one patches intended to make various structure elements constants, through use of the “const” keyword. The idea is that many kernel structures are already intended to be filled with consts because they contain mostly unmodified function pointers, and explicitly stating this helps the compiler to enforce it.
Super-H. Paul Mundt posted an update concerning features forthcoming for the Super-H (sh) architecture in 2.6.33. A lot of the work concerns newer parts with “relatively more complex and configurable cache features/topologies”, as well as an ongoing effort to migrate away from oprofile towards perf events.
Tracing. Jiri Olsa, obviously interested in speeding up kernel build time, took a look at Steven Rostedt’s “recordmcount.pl” scripts, that are used at compilation time to annotate kernel code with mcount callsite metadata. He decided to experiment with replacing the perl code with a compiled binary and has already achieved a two minute kernel compile time speedup. He isn’t sure whether he will continue with the work, but wanted to share his data anyway. Steven Rostedt followed up saying that John Reiser had already sent him some code that “convert[s] the entire shebang” and noting that he “like[s] that approach better”, and that he had just gotten back to looking into it.
In today’s announcements: Git version 1.6.5.5. Junio C Hamano announced the latest version of the GIT SCM favored by the kernel community has been released. Since the previous version, a number of issues have been addressed, including path handling “fixes”, diff behavior fixes, and so forth.
LTTng 0.181. Mathieu Desnoyers announced release 0.181 of LTTng targeting kernel 2.6.32 is now available at http://www.lttng.org/.
Pahole and the dwarves 1.8. Arnaldo Carvalho de Melo posted to let everyone know that the latest versions of his ELF binary examination utilities are now available in the pahole git tree on kernel.org.
Stable kernels 2.6.27.40 and 2.6.31.7. Greg Kroah-Hartman announced the availability of review patches for two forthcoming stable kernels. Comments should be provided no later than 20:00:00UTC on Tuesday December 8th.
The latest kernel release is 2.6.32.
Andrew Morton posted an mm-of-the-moment (mmotm) for 2009-12-03-22-57.
Stephen Rothwell posted a linux-next tree for December 4th. Since Thursday, the ext3 tree lost its build failure, the nfs tree gained a build failure so the previous day’s version was used, the block tree gained a build failures so the previous day’s version was used, the pcmcia tree gained a conflict against the net tree, the irda tree gained a conflict against the net tree, the limits tree gained conflicts against the net and fsnotify trees, the tip tree gained a conflict against the limits tree, and the sysctl tree gained 2 conflicts against the net tree. The total sub-tree count remained at 155, while Stephen also repeated his previous “call for calm” in not introducing items intended for 2.6.34 before 2.6.33-rc1 has been released.
Torok Edwin posted concerning some apparent bugs in the “perf” utilities, in particular with regard to the capture and replay of existing runs leading to a segmentation fault for which an example was provided.
That’s a summary of today’s Linux Kernel Mailing List traffic, for further information visit www.kernel.org. I’m Jon Masters.
